Ink jet printing is a well-known technique by which printing is accomplished without contact between the printing device and the substrate on which the printed characters are deposited. Briefly described, ink jet printing involves the technique of projecting a stream of ink droplets to a surface and controlling the direction of the stream, e.g., electronically, so that the droplets are caused to form the desired printed message on that surface.
The technique of ink jet printing or non-contact printing is particularly well suited for application of characters onto irregularly shaped substrates and surfaces, including, for example, glass, metal, or plastic containers, generally used for holding beverage, cosmetic, pharmaceutical, liquor, and health care products.
In general, an ink jet ink composition must meet certain requirements to be useful in ink jet printing operations. These relate to the viscosity and electrical resistivity of the ink jet ink composition, the solubility and compatibility of the components of the ink jet ink composition, and the wettability of the substrate by the ink jet ink composition. Further, the ink jet ink composition must be quick-drying and smear resistant; and the ink jet ink composition must be capable of passing through the ink jet nozzle or nozzles without clogging and permit rapid cleanup of the machine components with minimum effort. The printed message must have good adhesion and resist rubbing.
In addition, the ink jet ink composition must meet certain other requirements. Many beverage manufacturers fill the containers with chilled beverages, frequently under humid conditions that promote condensation of moisture on the containers. The moisture that condenses during printing on the container surfaces poses a severe problem in obtaining the desired ink penetration, good adhesion, and abrasion resistance of the printed messages. Thus, the ink jet ink composition should allow printing on these containers in the presence of a certain level of condensation, and the printed messages should not be damaged by the condensation. Further, when the containers are immersed in ice water for chilling or exposed to hot water during pasteurization, the printed messages should not disintegrate or be damaged by such treatments. Moreover, the bottles may be exposed to warm and humid conditions, e.g., during warehousing and shipping to different parts of the world and in different seasons. The messages should not be damaged by the hot and cold humid conditions. In addition, since many such containers are returned or redeemed for value, and reused, the messages on the containers should be removable by a caustic wash.
Ink jet ink compositions have been proposed for printing on glass substrates. However, these ink compositions have one or more drawbacks; for example, the ink dry time is excessively long or the ink composition is unsuitable for printing on dark colored glass substrates; or the printed message lacks sufficient adhesion to the substrate, resistance to damage by hot or cold water, or caustic washability.
The foregoing shows that there exists a need for an ink jet ink composition suitable for printing on glass substrates. The advantages of the present invention as well as additional inventive features will be apparent from the description of the invention provided herein.